Mike,
You could always go into Whitelist mode with the paid OpenDNS, where everything is off-limits, except what you explicitly enable. It does require that you start with a set of "safe" websites and add to them as your family runs into roadblocks. I've debated that, but since I'm mostly interested in blocking the ads and malicious sites, I'm happy with what I've got so far.
Of course, if your son is even slightly tech-aware, and has admin access to the box, all he has to do is put in Google's free DNS servers to bypass all your clever Net sanitizing.
Don,
If you're looking for a good 802.11N router, check out the Airport Extreme Dual Simultaneous Band base station over at the Apple Refurbished store. Paying $179 for a new unit is crazy, but $129 is a little less insane. The units go through QA checks that make sure they are as good as new and they come with a one-year warranty, too. In fact, when I took my Airport Extreme that I had picked up through the refurb'd store in to the Apple store to ask them to check it out, I ended up walking out with a brand new one. +100 for Customer Service.
I'm impressed with the Extreme's coverage. Even though it's in my basement, I get a good signal out on the street in front of my house. I had a Netgear 600-series before this (54G) and I had dead zones one the first floor of my house, let alone outside.
You can also configure a Guest Wi-Fi network that can be firewalled from the Home LAN, plus you can specify that guest units can't see each other. I haven't tried that feature yet, but with Christmas coming up, it might be enabled for all the nieces and nephews and their Wi-Fi capable mobile devices.